LOS ANGELES (Reuters) – Frederick Williams, a Marine Corps veteran scraping by on unemployment benefits, describes his living situation as "not homeless but close to it" and says he never cared enough to vote -- until Tuesday.

At age 43, Williams shuffled into a Los Angeles homeless shelter carrying his worldly belongings in a small travel case and a knotted plastic bag and proudly cast the first ballot of his life with guidance from poll workers.

Williams said he voted for Barack Obama, whose message of hope and bid to become the first black president of the United States stirred him like no other politician.

"This is history in the making. I wanted to be part of that," said Williams, who lives in a transient hotel a few blocks from the polling station at the Los Angeles Mission.

"For once in my lifetime ... someone really cares about the small people out there."

Williams was one of hundreds of people -- many first-time voters lacking permanent dwellings -- who cast ballots this year on Skid Row, a 50-block downtown area believed to harbor the highest concentration of homeless in the United States.

Those voters represent a fraction of the estimated 12,000 people who live and sleep on the streets of that area. Many are mentally ill or suffer from substance abuse.

But Orlando Ward, spokesman for the nearby Midnight Mission, said the numbers turning out on Tuesday were unprecedented. Some used the shelter's address to register, though a street corner can be listed as a place of residence.

"It's a very exciting to see people who are often forgotten and disenfranchised engaging in one of the most basic rights that we have as American citizens," Ward said. "In terms of interest and enthusiasm, it's at an all-time high."

By late morning, more than 300 voters, many of them homeless, had filed through the polling station at Midnight Mission, at least 10 times more than showed up all day during the last presidential election, he said.

Over 200 voters had cast ballots by noon at the Los Angeles Mission, said volunteer polling inspector Pamela Whitehead.

One of them was Andrew Wilson, 49, who lives on disability in a Skid Row hotel and was, too, moved by a sense of history.

"This is my first time voting," he said. "I want to be a part of the first African American being president."

Ward said he was struck by how caught up in politics many Skid Row residents appeared to be this year.

"There's a whole lot of T-shirts and hats with candidates' names on them worn by folks who don't have a lot of changes in clothes," he said.

(Editing by Mary Milliken and Philip Barbara)